Summary of Assumptions Used in Black-Scholes Option Pricing Model


	Three Months Ended		Nine Months Ended
	September 30,		September 30,
	2020	2019	2020	2019
Risk-free interest rate	0.35% - 0.43%	1.62%	0.35% - 1.57%	1.62% - 2.62%
Expected volatility	72.6% - 73.3%	71.8%	72.6% - 74.8%	71.8% - 75.2%
Expected dividend yield	0%	0%	0%	0%
Expected life of employee and Board options (in years)	6.25	6.25	6.25	6.25

A summary of stock option award activity related to employees, non-employee members of the Company’s Board of Directors and non-employee consultants as of and for the nine months ended September 30, 2020 is presented below:


		Weighted
	Number of	Average Exercise
	Shares	Price
Outstanding, December 31, 2019	4,450,517	$	14.73
Granted	1,165,350		16.40
Exercised	(52,493)		12.78
Expired	(170,581)		13.87
Forfeited	(127,151)		16.55
Outstanding, September 30, 2020	5,265,642	$	15.10
Options exercisable, September 30, 2020	2,960,041

Summary of Assumptions Used in Black-Scholes Option Pricing Model

On January 1, 2019, the Company used the Black-Scholes option valuation model to remeasure the fair value of all outstanding unvested options that had been granted to non-employee consultants in accordance with ASU 2018-07, Compensation – Stock Compensation (Topic 718), Improvements to Non-employee Share-Based Payment Accounting. The range of assumptions used by the Company on January 1, 2019 were as follows:



		January 1, 2019
Risk-free interest rate		2.59% - 2.62%
Expected volatility		58.9% - 84.6%
Expected dividend yield		0%
Expected life of non-employee options (in years)		0.81 - 8.19